DHCP Overrides

DHCP Overrides

Several DHCP behavior overrides are available. Most currently only have any
effect when using the networkd backend, with the exception of use-routes
and route-metric.

Overrides only have an effect if the corresponding dhcp4 or dhcp6 is
set to true.

If both dhcp4 and dhcp6 are true, the networkd backend requires
that dhcp4-overrides and dhcp6-overrides contain the same keys and
values. If the values do not match, an error will be shown and the network
configuration will not be applied.

When using the NetworkManager backend, different values may be specified for
dhcp4-overrides and dhcp6-overrides, and will be applied to the DHCP
client processes as specified in the netplan YAML.

dhcp4-overrides, dhcp6-overrides (mapping)

The dhcp4-overrides and dhcp6-overrides mappings override the
default DHCP behavior.

use-dns (bool)

Default: true. When true, the DNS servers received from the
DHCP server will be used and take precedence over any statically
configured ones. Currently only has an effect on the networkd
backend.

use-ntp (bool)

Default: true. When true, the NTP servers received from the
DHCP server will be used by systemd-timesyncd and take precedence
over any statically configured ones. Currently only has an effect on
the networkd backend.

send-hostname (bool)

Default: true. When true, the machine’s hostname will be sent
to the DHCP server. Currently only has an effect on the networkd
backend.

use-hostname (bool)

Default: true. When true, the hostname received from the DHCP
server will be set as the transient hostname of the system. Currently
only has an effect on the networkd backend.

use-mtu (bool)

Default: true. When true, the MTU received from the DHCP
server will be set as the MTU of the network interface. When false,
the MTU advertised by the DHCP server will be ignored. Currently only
has an effect on the networkd backend.

hostname (scalar)

Use this value for the hostname which is sent to the DHCP server,
instead of machine’s hostname. Currently only has an effect on the
networkd backend.

use-routes (bool)

Default: true. When true, the routes received from the DHCP
server will be installed in the routing table normally. When set to
false, routes from the DHCP server will be ignored: in this case,
the user is responsible for adding static routes if necessary for
correct network operation. This allows users to avoid installing a
default gateway for interfaces configured via DHCP. Available for
both the networkd and NetworkManager backends.

route-metric (scalar)

Use this value for default metric for automatically-added routes.
Use this to prioritize routes for devices by setting a lower metric
on a preferred interface. Available for both the networkd and
NetworkManager backends.

use-domains (scalar) – since 0.98

Takes a boolean, or the special value “route”. When true, the domain
name received from the DHCP server will be used as DNS search domain
over this link, similar to the effect of the Domains= setting. If set
to “route”, the domain name received from the DHCP server will be
used for routing DNS queries only, but not for searching, similar to
the effect of the Domains= setting when the argument is prefixed with
“~”.

Requires feature: dhcp-use-domains

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